With both hoists/cranes and conveyors they are designed to meet the exacting standards laid down by both British and International Standard Specifications inherent in which are the requirements regarding the safe working load that must be adhered to by the equipment at issue. If the safe working load or design capacity is exceeded, and particularly if it is exceeded repeatedly, it is not only inherently dangerous to operatives working in proximity to the equipment but also is a frequent cause of major breakdowns to the inconvenience and the cost of the user.
Historically, many attempts have been made to ensure that equipment of the kind mentioned above does not exceed its safe working load or design capacity, and a wide variety of rated capacity limiters (more usually referred to as "overload devices") have been proposed. With hoists/cranes they have for the most part been mechanical devices associated with the hoist/crane rope, and designed to react to the load on the rope. Also known to have been associated with the rope of hoists/cranes are linear transducers that also react to the load on the rope.
Other proposals have been to provide strain gauges by having a load cell linked direct to the load or a load pin fitted to a pulley of the hoist/crane or in the wheels of, e.g. a trolley for the movement of the hoist/crane on suspended tracks.
Predominantly, to date, such devices have only attended to the monitoring of the safe working loads.